The present invention relates to a laser survey instrument for forming a reference line or a reference plane by projecting a laser beam, and in particular to a laser survey instrument comprising a photodetector.
There are two types of laser survey instrument for forming a reference plane by rotary irradiation of a laser beam: a type using a visible light as a laser beam and the other type using an invisible light.
In the laser survey instrument using an invisible light as a laser beam, a photodetector is arranged at a position of an irradiation target, and an irradiation position of the laser beam is confirmed by the photodetector. Then, an index is marked at a position aligned with the irradiation position of the laser beam.
In the laser survey instrument using a visible light as a laser beam, a laser beam is directly projected to an irradiation plane, e.g. to an interior wall surface, and after visually confirming the irradiation position, an index is marked at a reference position. Also, on the laser survey instrument using a visible light as a laser beam, a photodetector is used in many cases.
Description is now given on a laser survey instrument referring to FIG. 7.
In this figure, reference numeral 1 represents a rotary laser device, and 2 represents a photodetector.
The rotary laser device 1 is installed using a tripod or other means (not shown). The rotary laser device 1 has a rotator 3, and a laser beam 4 is projected from the rotator 3 by rotary irradiation.
The photodetector 2 comprises a photodetection unit 5 for receiving the laser beam 4 and a display unit 6 for displaying a position of photodetection, and notches 7 are formed on each of lateral ends of the photodetector 2.
The photodetector 2 is supported on the irradiating position of the laser beam on a wall surface. When the laser beam 4 passes through it, the photodetection unit 5 detects the passing position. Based on the result of the detection by the photodetection unit 5, the display unit 6 displays that the irradiation position of the photodetector 2 with respect to the laser beam 4 is adequate. If it is not adequate, a direction deviated or a direction to be corrected is displayed by arrows 8. In case the position of the photodetector 2 is adequate, a mark is indicated using the notches 7. The mark thus indicated serves as an index of a reference position.
The marking operation as described above is based on the assumption that the rotary laser device 1 is properly leveled and that a reference plane formed by the laser beam 4 is horizontal. Therefore, if the rotary laser device 1 is tilted, the formed reference plane is also tilted, and the reference position is not aligned with the horizontal plane.
For this reason, in the conventional type laser survey instrument, the rotary laser device 1 is provided with display means 9, e.g. an alarm lamp to display status of the rotary laser device 1 such as tilting of the rotary laser device due to falling-down of the tripod caused by vibration. The display means 9 also displays information such as shortage of battery power.
In the conventional type laser survey instrument as described above, the photodetector 2 is normally used at a position considerably distant from the rotary laser device 1. As a result, even when there is trouble in the main unit and it is displayed by the alarm lamp on the display unit 9 of the main body, it is difficult to detect the alarm display from the position of the photodetector 2. Because the rotary laser device 1 is used for all-round rotation, there arises such a problem that the alarm display cannot be confirmed at all if direction of the display unit 9 of the main body is deviated due to the direction of the rotary laser device 1.
Further, in case a wireless equipment is incorporated and used instead of the display unit of the rotary laser device 1, there is limitation to radio frequency and power supply. That is, the used frequency varies according to each country, and there are problems in that much power is required for wireless equipment and a battery of large capacity is needed. There is an alternative way, i.e. to modulate the frequency and to transmit the information to the photodetector 2 via the laser beam. However, frequency modulation must be considerably high depending on the number of rotations and on the size of the photodetection unit of the photodetector 2, and it may be technically difficult or power consumption may increase.